Method for supercritical processing of multiple workpieces

ABSTRACT

An apparatus for supercritical processing of multiple workpieces comprises a transfer module, first and second supercritical processing modules, and a robot. The transfer module includes an entrance. The first and second supercritical processing modules are coupled to the transfer module. The robot is preferably located with the transfer module. In operation, the robot transfers a first workpiece from the entrance of the transfer module to the first supercritical processing module. The robot then transfers a second workpiece from the entrance to the second supercritical processing module. After the workpieces have been processed, the robot returns the first and second workpieces to the entrance of the transfer module. Alternatively, the apparatus includes additional supercritical processing modules coupled to the transfer module.

RELATED APPLICATIONS

[0001] This application claims priority from U.S. Provisional PatentApplication No. 60/163,121 filed on Nov. 2, 1999, which is incorporatedby reference.

FIELD OF THE INVENTION

[0002] This invention relates to the field of supercritical processing.More particularly, this invention relates to the field of supercriticalprocessing where multiple workpieces are processed simultaneously.

BACKGROUND OF THE INVENTION

[0003] Semiconductor fabrication uses photoresist in ion implantation,etching, and other processing steps. In the ion implantation steps, thephotoresist masks areas of a semiconductor substrate that are notimplanted with a dopant. In the etching steps, the photoresist masksareas of the semiconductor substrate that are not etched. Examples ofthe other processing steps include using the photoresist as a blanketprotective coating of a processed wafer or the blanket protectivecoating of a MEMS (micro electromechanical system) device. Following theion implantation steps, the photoresist exhibits a hard outer crustcovering a jelly-like core. The hard outer crust leads to difficultiesin a photoresist removal. Following the etching steps, remainingphotoresist exhibits a hardened character that leads to difficulties inthe photoresist removal. Following the etching steps, residue(photoresist residue mixed with etch residue) coats sidewalls of etchfeatures. Depending on a type of etching step and material etched, thephotoresist residue mixed with the etch residue presents a challengingremoval problem since the photoresist residue mixed with the etchresidue often strongly bond to the sidewalls of the etch features.

[0004] Typically, in the prior art, the photoresist and the residue areremoved by plasma ashing in an O₂ plasma followed by cleaning in awet-clean bath. A semiconductor etching and metallization process of theprior art is illustrated in block diagram format in FIG. 1. Thesemiconductor etching and metallization process 10 includes aphotoresist application step 12, a photoresist exposure step 14, aphotoresist development step 16, a dielectric etch step 18, an ashingstep 20, a wet cleaning step 22, and a metal deposition step 24. In thephotoresist application step 12, the photoresist is applied to a waferhaving an exposed oxide layer. In the photoresist exposure step 14, thephotoresist is exposed to light which is partially blocked by a mask.

[0005] Depending upon whether the photoresist is a positive or negativephotoresist, either exposed photoresist or non-exposed photoresist,respectively, is removed in the photoresist development step 16 leavinga exposed pattern on the oxide layer. In the dielectric etch step 18,the exposed pattern on the oxide layer is etched in an RIE (reactive ionetch) process which etches the exposed pattern into the oxide layer,forming an etched pattern, while also partially etching the photoresist.This produces the residue which coats the sidewalls of the etch featureswhile also hardening the photoresist. In the ashing step 20, the O₂plasma oxidizes and partially removes the photoresist and the residue.In the wet cleaning step 22, remaining photoresist and residue iscleaned in the wet-clean bath.

[0006] In the metal deposition step 24, a metal layer is deposited onthe wafer filling the etched pattern and also covering non-etchedregions. In subsequent processing, at least part of the metal coveringthe non-etched regions is removed in order to form a circuit.

[0007] Nishikawa et al. in U.S. Pat. No. 4,944,837, issued on Jul. 31,1990, recite a prior art method of removing a resist using liquidized orsupercritical gas. A substrate with the resist is placed into a pressurevessel, which also contains the liquidized or supercritical gas. After apredetermined time lapse, the liquidized or supercritical gas is rapidlyexpanded, which removes the resist.

[0008] Nishikawa et al. teach that supercritical CO₂ can be used as adeveloper for photoresist. A substrate with a photoresist layer isexposed in a pattern to light, thus forming a latent image. Thesubstrate with the photoresist and the latent image is placed in asupercritical CO₂ bath for 30 minutes. The supercritical CO₂ is thencondensed leaving the pattern of the photoresist. Nishikawa et al.further teach that 0.5% by weight of methyl isobutyl ketone (MIBK) canbe added to the supercritical CO₂, which increases an effectiveness ofthe supercritical CO₂ and, thus, reduces a development time from the 30minutes to 5 minutes. Nishikawa et al. also teach that a photoresist canbe removed using the supercritical CO₂ and 7% by weight of the MIBK. Thesubstrate with the photoresist is placed in the supercritical CO₂ andthe MIBK for 30-45 minutes. Upon condensing the supercritical CO₂, thephotoresist has been removed.

[0009] The methods taught by Nishikawa et al. are inappropriate for asemiconductor fabrication line for a number of reasons. Rapidlyexpanding a liquidized or supercritical gas to remove a photoresist froma substrate creates a potential for breakage of the substrate. Aphotoresist development process which takes 30 minutes is tooinefficient. A photoresist development or removal process which usesMIBK is not preferred because MIBK is toxic and because MIBK is usedonly when a more suitable choice is unavailable.

[0010] Smith, Jr. et al. in U.S. Pat. No. 5,377,705, issued on Jan. 3,1995, teach a system for cleaning contaminants from a workpiece. Thecontaminants include organic, particulate, and ionic contaminants. Thesystem includes a pressurizable cleaning vessel, a liquid CO₂ storagecontainer, a pump, a solvent delivery system, a separator, a condenser,and various valves. The pump transfers CO₂ gas and solvent to thecleaning vessel and pressurizes the CO₂ gas to supercritical CO₂. Thesupercritical CO₂ and the solvent remove the contaminants from theworkpiece. A valve allows some of the supercritical CO₂ and the solventto bleed from the cleaning vessel while the pump replenishes thesupercritical CO₂ and the solvent. The separator separates the solventfrom the supercritical CO₂. The condenser condenses the CO₂ to liquidCO₂ so that the liquid CO₂ storage container can be replenished.

[0011] Employing a system such as taught by Smith, Jr. et al. forremoving photoresist and residue presents a number of difficulties. Thepressurizable cleaning vessel is not configured appropriately forsemiconductor substrate handling. It is inefficient to bleed thesupercritical CO₂ and the solvent during cleaning. Such a system is notreadily adaptable to throughput requirements of a semiconductorfabrication line. Such a system is not conducive to safe semiconductorsubstrate handling, which is crucial in a semiconductor fabricationline. Such a system is not economical for semiconductor substrateprocessing.

[0012] What is needed is a method of developing photoresist usingsupercritical carbon dioxide appropriate for a semiconductor fabricationline.

[0013] What is needed is a method of removing photoresist usingsupercritical carbon dioxide appropriate for a semiconductor fabricationline.

[0014] What is needed is a supercritical processing system which isconfigured for handling semiconductor substrates.

[0015] What is needed is a supercritical processing system in whichsupercritical CO₂ and solvent are not necessarily bled from a processingchamber in order to create a fluid flow within the processing chamber.

[0016] What is needed is a supercritical processing system which meetsthroughput requirements of a semiconductor fabrication line.

[0017] What is needed is a supercritical processing system whichprovides safe semiconductor substrate handling.

[0018] What is needed is a supercritical processing system whichprovides economical semiconductor substrate processing.

SUMMARY OF THE INVENTION

[0019] The present invention is an apparatus for supercriticalprocessing of multiple workpieces. The apparatus includes a transfermodule, first and second supercritical processing modules, and a robot.The transfer module includes an entrance. The first and secondsupercritical processing modules are coupled to the transfer module. Therobot is preferably located within the transfer module. In operation,the robot transfers a first workpiece from the entrance of the transfermodule to the first supercritical processing module. The robot thentransfers a second workpiece from the entrance to the secondsupercritical processing module. After the workpieces have beenprocessed, the robot returns the first and second workpieces to theentrance of the transfer module. Alternatively, the apparatus includesadditional supercritical processing modules coupled to the transfermodule.

BRIEF DESCRIPTION OF THE DRAWINGS

[0020]FIG. 1 illustrates, in block diagram format, a process flow for asemiconductor etching and metallization process of the prior art.

[0021]FIG. 2 illustrates, in block diagram format, a process flow for asemiconductor etching and metallization process of the presentinvention.

[0022]FIG. 3 illustrates, in block diagram format, a supercriticalremoval process of the present invention.

[0023]FIG. 4 illustrates the preferred supercritical processing systemof the present invention.

[0024]FIG. 5 illustrates the preferred supercritical processing moduleof the present invention.

[0025]FIG. 6 illustrates a first alternative supercritical processingsystem of the present invention.

[0026]FIG. 7 illustrates a second alternative supercritical processingsystem of the present invention.

[0027]FIG. 8 illustrates a third alternative supercritical processingsystem of the present invention.

[0028]FIG. 9 illustrates a fourth alternative supercritical processingsystem of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0029] A semiconductor etch and metallization process of the presentinvention is illustrated, as a block diagram, in FIG. 2. Thesemiconductor etch and metallization process 30 includes a photoresistapplication step 32, a photoresist exposure step 34, a photoresistdevelopment step 36, a dielectric etch step 38, a supercritical removalprocess 40, and a metal deposition step 42. In the photoresistapplication step 32, the photoresist is applied to a wafer having anexposed oxide layer. In the photoresist exposure step 34, thephotoresist is exposed to light which is partially blocked by a mask.

[0030] Depending upon whether the photoresist is a positive or negativephotoresist, either exposed photoresist or non-exposed photoresist,respectively, is removed in the photoresist development step 36 leavinga exposed pattern on the oxide layer. In the dielectric etch step 38,the exposed pattern on the oxide layer is preferably etched in an RIE(reactive ion etch) process which etches the exposed pattern into theoxide layer while also partially etching the photoresist. This producesthe residue which coats the sidewalls of the etch features while alsohardening the photoresist.

[0031] In the supercritical removal process 40, supercritical carbondioxide and a solvent are used to remove the photoresist and theresidue. In the metal deposition step 42, a metal layer is deposited onthe wafer filling the etched pattern and also covering non-etchedregions. In subsequent processing, at least part of the metal coveringthe non-etched regions is removed in order to form a circuit.

[0032] The supercritical removal process 40 of the present invention isillustrated, as a block diagram, in FIG. 3. The supercritical removalprocess 40 begins by placing the wafer, with the photoresist and theresidue on the wafer, within a pressure chamber and sealing the pressurechamber in a first process step 52. In a second process step 54, thepressure chamber is pressurized with carbon dioxide until the carbondioxide becomes the supercritical carbon dioxide (SCCO₂). In a thirdprocess step 56, the supercritical carbon dioxide carries a solvent intothe process chamber. In a fourth process step 58, the supercriticalcarbon dioxide and the solvent are maintained in contact with the waferuntil the photoresist and the residue are removed from the wafer. In thefourth process step 58, the solvent at least partially dissolves thephotoresist and the residue. In a fifth process step 60, the pressurechamber is partially exhausted. In a sixth process step 62, the wafer isrinsed. In a seventh process step 64, the supercritical removal process40 ends by depressurizing the pressure chamber and removing the wafer.

[0033] The supercritical removal process 40 is preferably implemented ina semiconductor fabrication line by the preferred supercriticalprocessing system of the present invention, which is illustrated in FIG.4. The preferred supercritical processing system 70 includes a transfermodule 72, first through fifth supercritical processing modules, 74-78,a robot 80, and control electronics 82. The transfer module includesfirst through fifth process ports, 84-88, and a transfer module entrance90. The transfer module entrance 90 includes first and second hand-offstations, 92 and 94, and first and second entrance ports, 96 and 98.

[0034] The first through fifth supercritical processing modules, 74-78,are coupled to the transfer module 72 via the first through fifthprocess ports, 84-88, respectively. Preferably, the robot 80 is coupledto the transfer module 72 at a center of the transfer module 72. Thefirst and second hand-off stations, 92 and 94, are coupled to thetransfer module via the first and second entrance ports, 96 and 98,respectively. The control electronics 82 are coupled to the transfermodule 72.

[0035] Preferably, the transfer module 72 operates at atmosphericpressure. Alternatively, the transfer module 72 operates at a slightpositive pressure relative to a surrounding environment where the slightpositive pressure is produced by an inert gas injection arrangement. Theinert gas injection arrangement injects an inert gas, such as Ar, CO₂,or N₂, into the transfer module 72. This assures a cleaner processingenvironment within the transfer module 72.

[0036] The robot 80 preferably includes a robot base 100, a robot arm102, and an end effector 104. The robot base is coupled to the transfermodule 72. The robot arm 102 is preferably a two piece robot arm, whichcouples the end effector 104 to the robot base 100. The end effector 104is configured to pick and place workpieces. Preferably, the end effector104 is configured to pick and place the wafer. Alternatively, the endeffector 104 is configured to pick and place a puck or other substrate.Alternatively, a dual arm robot replaces the robot 80, where the dualarm robot includes two arms and two end effectors.

[0037] The first through fifth supercritical processing modules, 74-78,preferably include first through fifth gate valves, 106-110,respectively. The first through fifth gate valves, 106-110, couple firstthrough fifth workpiece cavities, 112-116, of the first through fifthsupercritical processing modules, 74-78, respectively, to the firstthrough fifth process ports, 84-88.

[0038] Preferably, in operation, the robot 80 transfers a firstworkpiece 118 from the first hand-off station 92 to the firstsupercritical processing module 74, where the supercritical removalprocess 40 is performed. Subsequently, the robot 80 transfers a secondworkpiece 120 from the first hand-off station 92 to the secondsupercritical processing module 75, where the supercritical removalprocess 40 is performed. Further, the robot 80 transfers third throughfifth workpieces (not shown) from the first hand-off station 92 to thethird through fifth supercritical processing modules, 76-78,respectively, where the supercritical removal process 40 is performed.

[0039] In subsequent operation, the robot 80 transfers the firstworkpiece from the first supercritical processing module 74 to thesecond hand-off station 94. Further, the robot 80 transfers the secondworkpiece from the second supercritical processing module 75 to thesecond hand-off station 94. Moreover, the robot 80 transfers the thirdthrough fifth workpieces from the third through fifth supercriticalprocessing modules, 76-78, respectively, to the second hand-off station94.

[0040] Preferably, the first workpiece 118, the second wafer 120, andthe third through fifth workpieces are wafers. Preferably, the wafersare in a first cassette at the first handoff station 92 prior tosupercritical processing. Preferably, the wafers are placed by the robot80 in a second cassette at the second hand-off station 94 following thesupercritical processing. Alternatively, the wafers begin and end in thefirst cassette at the first handoff station 92 along while a secondgroup of wafers begins and ends in the second cassette at the secondhand-off station 94.

[0041] It will be readily apparent to one skilled in the art that thesecond hand-off station 94 can be eliminated or that additional hand-offstations can be added to the preferred supercritical processing system70. Further, it will be readily apparent to one skilled in the art thatthe preferred supercritical processing system 70 can be configured withless than the first through fifth supercritical processing modules,74-78, or more than the first through fifth supercritical processingmodules, 74-78. Moreover, it will be readily apparent to one skilled inthe art that the robot 80 can be replaced by a transfer mechanism whichis configured to transfer the first workpiece 118, the second workpiece120, and the third through fifth workpieces. Additionally, it will bereadily apparent to one skilled in the art that the first and secondcassettes can be front opening unified pods which employ a standardmechanical interface concept so that the wafers can be maintained in aclean environment separate from the surrounding environment.

[0042] The first supercritical processing module 74 of the presentinvention is illustrated in FIG. 5. The first supercritical processingmodule 74 includes a carbon dioxide supply vessel 132, a carbon dioxidepump 134, the pressure chamber 136, a chemical supply vessel 138, acirculation pump 140, and an exhaust gas collection vessel 144. Thecarbon dioxide supply vessel 132 is coupled to the pressure chamber 136via the carbon dioxide pump 134 and carbon dioxide piping 146. Thecarbon dioxide piping 146 includes a carbon dioxide heater 148 locatedbetween the carbon dioxide pump 134 and the pressure chamber 136. Thepressure chamber 136 includes a pressure chamber heater 150. Thecirculation pump 140 is located on a circulation line 152, which couplesto the pressure chamber 136 at a circulation inlet 154 and at acirculation outlet 156. The chemical supply vessel 138 is coupled to thecirculation line 152 via a chemical supply line 158, which includes afirst injection pump 159. A rinse agent supply vessel 160 is coupled tothe circulation line 152 via a rinse supply line 162, which includes asecond injection pump 163. The exhaust gas collection vessel 144 iscoupled to the pressure chamber 136 via exhaust gas piping 164.

[0043] The carbon dioxide supply vessel 132, the carbon dioxide pump134, and the carbon dioxide heater 148 form a carbon dioxide supplyarrangement 149. The chemical supply vessel 138, the first injectionpump 159, the rinse agent supply vessel 160, and the second injectionpump 163 form a chemical and rinse agent supply arrangement 165.Preferably, the carbon dioxide supply arrangement 149, the chemical andrinse agent supply arrangement 165, and the exhaust gas collectionvessel 144 service the second through fifth supercritical processingmodules, 75-78, (FIG. 3) as well as the first supercritical processingmodule 74. In other words, preferably, the first supercriticalprocessing module 74 includes the carbon dioxide supply arrangement 149,the chemical and rinse agent supply arrangement 165, and the exhaust gascollection vessel 144 while the second through fifth supercriticalprocessing modules, 75-78, share the carbon dioxide supply arrangement149, the chemical and rinse agent supply arrangement 165, and theexhaust gas collection vessel 144 of the first supercritical processingmodule 74.

[0044] It will be readily apparent to one skilled in the art that one ormore additional carbon dioxide supply arrangements, one or moreadditional chemical and rinse agent supply arrangements, or one or moreadditional exhaust gas collection vessels can be provided to service thesecond through fifth supercritical processing modules, 75-78. Further,it will be readily apparent to one skilled in the art that the firstsupercritical processing module 74 includes valving, controlelectronics, filters, and utility hookups which are typical ofsupercritical fluid processing systems. Moreover, it will be readilyapparent to one skilled in the art that additional chemical supplyvessels could be coupled to the first injection pump 159 or that theadditional chemical supply vessels and additional injection pumps couldbe coupled to the circulation line 152.

[0045] Referring to FIGS. 3, 4, and 5, implementation of thesupercritical removal method 40 begins with the first process step 52,in which the wafer, having the photoresist or the residue (or both thephotoresist and the residue) is inserted through the first process portand placed in the first wafer cavity 112 of the pressure chamber 136 bythe robot 80 and, then, the pressure chamber 136 is sealed by closingthe gate valve 106. In the second process step 54, the pressure chamber136 is pressurized by the carbon dioxide pump 134 with the carbondioxide from the carbon dioxide supply vessel 132. During the secondstep 54, the carbon dioxide is heated by the carbon dioxide heater 148while the pressure chamber 136 is heated by the pressure chamber heater150 to ensure that a temperature of the carbon dioxide in the pressurechamber 136 is above a critical temperature. The critical temperaturefor the carbon dioxide is 31° C. Preferably, the temperature of thecarbon dioxide in the pressure chamber 136 is within a range of 45° C.to 75° C. Alternatively, the temperature of the carbon dioxide in thepressure chamber 136 is maintained within a range of from 31° C. toabout 100° C.

[0046] Upon reaching initial supercritical conditions, the firstinjection pump 159 pumps the solvent from the chemical supply vessel 138into the pressure chamber 136 via the circulation line 152 while thecarbon dioxide pump further pressurizes the supercritical carbon dioxidein the third process step 56. At a beginning of a solvent injection, thepressure in the pressure chamber 136 is about 1,100-1,200 psi. Once adesired amount of the solvent has been pumped into the pressure chamber136 and desired supercritical conditions are reached, the carbon dioxidepump 134 stops pressurizing the pressure chamber 136, the firstinjection pump 159 stops pumping the solvent into the pressure chamber136, and the circulation pump 140 begins circulating the supercriticalcarbon dioxide and the solvent in the fourth process step 58.Preferably, the pressure at this point is about 2,700-2,800 psi. Bycirculating the supercritical carbon dioxide and the solvent, thesupercritical carbon dioxide maintains the solvent in contact with thewafer. Additionally, by circulating the supercritical carbon dioxide andthe solvent, a fluid flow enhances removal of the photoresist and theresidue from the wafer.

[0047] Preferably, the wafer is held stationary in the pressure chamber136 during the fourth process step 58. Alternatively, the wafer is spunwithin the pressure chamber 136 during the fourth process step 58.

[0048] After the photoresist and the residue has been removed from thewafer, the pressure chamber 136 is partially depressurized by exhaustingsome of the supercritical carbon dioxide, the solvent, removedphotoresist, and removed residue to the exhaust gas collection vessel144 in order to return conditions in the pressure chamber 136 to nearthe initial supercritical conditions in the fifth process step 60.Preferably, the pressure within the pressure chamber 136 is cycled atleast once at this point by raising the pressure and then againpartially exhausting the pressure chamber 136. This enhances acleanliness within the pressure chamber 136. In the fifth process step60, the pressure chamber is preferably maintained above the criticaltemperature and above a critical pressure. The critical pressure forcarbon dioxide is 1,070 psi.

[0049] In the sixth process step 62, the second injection pump 163 pumpsa rinse agent from the rinse agent supply vessel 160 into the pressurechamber 136 via the circulation line while the carbon dioxide pump 134pressurizes the pressure chamber 136 to near the desired supercriticalconditions and, then, the circulation pump 140 circulates thesupercritical carbon dioxide and the rinse agent in order to rinse thewafer. Preferably, the rinse agent is selected from the group consistingof water, alcohol, acetone, and a mixture thereof. More preferably, therinse agent is the mixture of the alcohol and the water. Preferably, thealcohol is selected from the group consisting of isopropyl alcohol,ethanol, and other low molecular weight alcohols. More preferably, thealcohol is selected from the group consisting of the isopropyl alcoholand the ethanol. Most preferably, the alcohol is the ethanol.

[0050] Preferably, the wafer is held stationary in the pressure chamber136 during the sixth process step 62. Alternatively, the wafer is spunwithin the pressure chamber 136 during the sixth process step 62.

[0051] In the seventh process step 64, the pressure chamber 136 isdepressurized, by exhausting the pressure chamber 136 to the exhaust gascollection vessel 144, the gate valve 106 is opened, and the wafer isremoved from the pressure chamber 136 by the robot 80.

[0052] Alternative supercritical removal processes of the presentinvention are taught in the following patent applications, all of whichare incorporated in their entirety by reference: U.S. Patent Application(Attorney Docket No. SSI-00103), filed on Oct. 25, 2000; U.S. patentapplication Ser. No. 09/389,788, filed on Sep. 3, 1999; U.S. patentapplication Ser. No. 09/085,391, filed on May 27, 1998; and U.S.Provisional Patent Application No. 60/047,739, filed May 27, 1997.

[0053] A first alternative supercritical processing system of thepresent invention is illustrated in FIG. 6. The first alternativesupercritical processing system 170 adds first through fifthante-chambers, 172-176, and first through fifth ante-chamber robots,178-182, to the preferred supercritical processing system 70. Inoperation, the first through fifth ante-chambers, 172-176, operate fromabout atmospheric pressure to some elevated pressure. This allows thefirst through fifth wafer cavities, 112-16, to operate between theelevated pressure and supercritical pressure and, thus, enhancingthroughput. Alternatively, in the first alternative supercriticalprocessing system 170, the first through fifth ante-chamber robots,178-182, are replaced with first through fifth magnetically coupledmechanisms, or first through fifth hydraulically driven mechanisms, orfirst through fifth pneumatically driven mechanisms.

[0054] A second alternative supercritical processing system of thepresent invention of the present invention is illustrated in FIG. 7. Thesecond alternative supercritical processing system 190 replaces thefirst and second hand-off stations, 92 and 94, of the preferredsupercritical processing system 70 with first and second loadlocks, 192and 194. In operation, the transfer module operates at a second elevatedpressure and, thus, also enhances the throughput.

[0055] A third alternative supercritical processing system of thepresent invention of the present invention is illustrated in FIG. 8. Thethird alternative supercritical processing system 200 comprises analternative transfer module 202 and a robot track 204.

[0056] A fourth alternative supercritical processing system of thepresent invention is illustrated in FIG. 9. The fourth alternativesupercritical processing system 210 preferably replaces the thirdsupercritical processing module 76 of the preferred supercriticalprocessing system 70 with a third hand-off station 212 and adds a secondtransfer module 214, a second robot 216, and additional supercriticalprocessing modules 218. In the fourth alternative supercriticalprocessing system 210, the third hand-off station 212 couples thetransfer module 72 to the second transfer module 214. The second robot216 preferably resides in the second transfer module 214. The additionalsupercritical processing modules 218 are coupled to the second transfermodule 214. Thus, the fourth alternative supercritical processing system210 allows for more supercritical processing modules than the preferredsupercritical processing system 70.

[0057] A fifth alternative supercritical processing system of thepresent invention eliminates the transfer module 72 of the preferredsupercritical processing system 70. In the fifth alternativesupercritical processing system, the robot 80 is configured to moveworkpieces between the first and second hand-off stations, 92 and 94,and the first through fifth supercritical processing modules, 74-78,without benefitting from a covering effect provided by the transfermodule 72.

[0058] A sixth alternative supercritical processing system of thepresent invention adds an inspection station to the preferredsupercritical processing system 70. In the sixth alternativesupercritical processing system, the first workpiece 118, the secondworkpiece 120, and the third through fifth workpieces are transferred tothe inspection station prior to being transferred to the second hand-offstation 94. At the inspection station, an inspection of the workpiecesensures that the photoresist and the residue have been removed from theworkpieces. Preferably, the inspection station uses spectroscopy toinspect the workpieces.

[0059] A seventh alternative supercritical processing system of thepresent invention adds a front-end robot to the preferred supercriticalprocessing system 70. In the seventh alternative supercriticalprocessing system, the front-end robot resides outside of the entranceto the transfer module 72 and the first and second cassettes are locatedaway from the first and second hand-off stations, 92 and 94. Thefront-end robot is preferably configured to move the wafers from thefirst cassette to the first hand-off station 92 and is also preferablyconfigured to move the wafers from the second hand-off station 94 to thesecond cassette.

[0060] An eighth alternative supercritical processing system of thepresent invention adds a wafer orientation mechanism to the preferredsupercritical processing system 70. The wafer orientation mechanismorients the wafer according to a flat, a notch, or an other orientationindicator. Preferably, the wafer is oriented at the first hand-offstation 92. Alternatively, the wafer is oriented at the second hand-offstation 94.

[0061] A first alternative supercritical processing module of thepresent invention replaces the pressure chamber 136 and gate valve 106with an alternative pressure chamber. The alternative pressure chambercomprises a chamber housing and a hydraulicly driven wafer platen. Thechamber housing comprises a cylindrical cavity which is open at itsbottom. The hydraulicly driven wafer platen is configured to sealagainst the chamber housing outside of the cylindrical cavity. Inoperation, the wafer is placed on the hydraulicly driven wafer platen.Then, the hydraulicly driven wafer platen moves upward and seals withthe chamber housing. Once the wafer has been processed. the hydrauliclydriven wafer platen is lowered and the wafer is taken away.

[0062] A second alternative supercritical processing module of thepresent invention places alternative inlets for the circulation line 152to enter the wafer cavity 112 at a circumference of the wafer cavity 112and places an alternative outlet at a top center of the wafer cavity112. The alternative inlets are preferably configured to inject thesupercritical carbon dioxide in a plane defined by the wafer cavity 112.Preferably, the alternative inlets are angled with respect to a radiusof the wafer cavity 112 so that in operation the alternative inlets andthe alternative outlet create a vortex within the wafer cavity 112.

[0063] It will be readily apparent to one skilled in the art that othervarious modifications may be made to the preferred embodiment withoutdeparting from the spirit and scope of the invention as defined by theappended claims.

We claim:
 1. An apparatus for supercritical processing of first andsecond workpieces comprising: a. a transfer module having an entrance;b. first and second supercritical processing modules coupled to thetransfer module; and c. a transfer mechanism coupled to the transfermodule, the transfer mechanism configured to move the first workpiecebetween the entrance and the first supercritical processing module, thetransfer mechanism configured to move the second workpiece between theentrance and the second supercritical processing module.
 2. Theapparatus of claim 1 wherein the transfer module operates at aboutatmospheric pressure.
 3. The apparatus of claim 1 wherein the transfermodule further comprises means for maintaining a slight positivepressure in the transfer module relative to a surrounding environment.4. The apparatus of claim 3 wherein the means for maintaining the slightpositive pressure in the transfer module comprise an inert gas injectionarrangement.
 5. The apparatus of claim 2 wherein the entrance of thetransfer module comprises a hand-off station.
 6. The apparatus of claim5 wherein the entrance of the transfer module further comprises anadditional hand-off station.
 7. The apparatus of claim 1 wherein thetransfer module operates at an elevated pressure and further wherein theentrance of the transfer module comprises a loadlock.
 8. The apparatusof claim 7 wherein the entrance of the transfer module further comprisesan additional loadlock.
 9. The apparatus of claim 1 wherein the transfermechanism comprises a robot.
 10. The apparatus of claim 9 wherein thetransfer module comprises a circular configuration.
 11. The apparatus ofclaim 10 wherein the robot comprises a central robot, the central robotoccupying a center of the circular configuration.
 12. The apparatus ofclaim 9 wherein the transfer module comprises a track configuration. 13.The apparatus of claim 12 wherein the robot comprises a tracked robot,the tracked robot comprising the robot coupled to a track such that therobot moves along the track in order to reach the first and secondprocessing module located along the track.
 14. The apparatus of claim 13further comprising third and fourth supercritical processing modules,the third and fourth supercritical processing modules located along thetrack, the third and fourth supercritical processing modules locatedopposite the first and second supercritical processing modules relativeto the track.
 15. The apparatus of claim 9 wherein the robot comprisesan extendable arm and an end effector.
 16. The apparatus of claim 15wherein the robot further comprises an additional arm and an additionalend effector.
 17. The apparatus of claim 1 wherein the firstsupercritical processing module comprises a first pressure vessel andfurther wherein the second supercritical processing module comprises asecond pressure vessel.
 18. The apparatus of claim 17 wherein: a. thefirst pressure vessel comprises a first workpiece cavity and a firstpressure vessel entrance, the first workpiece cavity holding the firstworkpiece during supercritical processing, the first pressure vesselentrance providing ingress and egress for the first workpiece; and b.the second pressure vessel comprises a second workpiece cavity and asecond pressure vessel entrance, the second workpiece cavity holding thesecond workpiece during the supercritical processing, the secondpressure vessel entrance providing ingress and egress for the firstworkpiece.
 19. The apparatus of claim 18 wherein the transfer mechanismis configured to place the first and second workpieces in the first andsecond workpiece cavities, respectively.
 20. The apparatus of claim 19wherein the transfer module and the supercritical processing module areconfigured to operate at supercritical conditions.
 21. The apparatus ofclaim 19 further comprising first and second gate valves, the first gatevalve coupling the transfer module and the first supercriticalprocessing module, the second gate valve coupling the transfer moduleand the second supercritical processing module.
 22. The apparatus ofclaim 18 further comprising first and second antechambers, the firstante-chamber coupling the transfer module and the first supercriticalprocessing module, the second ante-chamber coupling the transfer moduleand the second supercritical processing module.
 23. The apparatus ofclaim 1 further comprising means for pressurizing the first and secondsupercritical processing modules.
 24. The apparatus of claim 23 whereinthe means for pressurizing comprises a CO₂ pressurizing configurationwhich comprises a CO₂ supply vessel coupled to a pump which is coupledto the first and second supercritical processing modules such that theCO₂ pressurizing configuration pressurizes the first supercriticalprocessing module independently of the second supercritical processingmodule and further such that the CO₂ pressurizing configurationpressurizes the second supercritical processing module independently ofthe first supercritical processing module.
 25. The apparatus of claim 18further comprising first and second means for sealing, the first meansfor sealing operable to seal the first pressure vessel entrance, thesecond means for sealing operable to seal the second pressure vesselentrance.
 26. The apparatus of claim 1 further comprising means forcontrolling such that the means for controlling directs the transfermechanism to move the first and second workpieces between the entranceof the transfer module and the first and second supercritical processingmodules, respectively, and further such that the means for controllingcontrols the first supercritical processing module independently of thesecond supercritical processing module.
 27. A method of supercriticalprocessing first and second workpieces comprising the steps of: a.transferring the first workpiece from an entrance of a transfer moduleto a first supercritical processing module; b. transferring the secondworkpiece from the entrance of the transfer module to a secondsupercritical processing module; c. processing the first and secondworkpieces in the first and second supercritical processing modules,respectively; d. transferring the first workpiece from the firstsupercritical processing module to the entrance of the transfer module;and e. transferring the second workpiece from the second supercriticalprocessing module to the entrance of the transfer module.
 28. The methodof claim 27 wherein the entrance of the transfer module comprises ahand-off station.
 29. The method of claim 28 wherein the entrance of thetransfer module further comprises an additional hand-off station.
 30. Anapparatus for supercritical processing first and second workpiecescomprising: a. means for transferring the first and second workpieces;b. first means for supercritical processing configured such that inoperation the means for transferring transfers the first workpiecebetween an entrance of a transfer module to the first means forsupercritical processing and further such that in operation the firstmeans for supercritical processing processes the first workpiece; and c.second means for supercritical processing configured such that inoperation the means for transferring transfers the second workpiecebetween the entrance of the transfer module to the second means forsupercritical processing and further such that in operation the secondmeans for supercritical processing processes the second workpiece. 31.An apparatus for supercritical processing comprising: a. a transfermodule having an entrance; b. an inert gas injection arrangement coupledto the transfer module such that in operation the inert gas injectionarrangement maintains a slight positive pressure in the transfer modulerelative to a surrounding environment; c. a first ante-chamber coupledto the transfer module; d. a first supercritical processing modulecoupled to the first ante-chamber; e. first means for moving a firstsemiconductor substrate between the first ante-chamber and the firstsupercritical processing module; f. a second ante-chamber coupled to thetransfer module; g. a second supercritical processing module coupled tothe second ante-chamber; h. second means for moving a secondsemiconductor substrate between the second ante-chamber and the secondsupercritical processing module; and i. a transfer mechanism coupled tothe transfer module such that in operation the transfer mechanismtransfers the first and second semiconductor substrates between thefirst and second ante-chambers, respectively, and the entrance of thetransfer module.
 32. An apparatus for supercritical processingcomprising: a. a transfer module having an entrance; b. an inert gasinjection arrangement coupled to the transfer module such that inoperation the inert gas injection arrangement maintains a slightpositive pressure in the transfer module relative to a surroundingenvironment; c. a first supercritical processing module coupled to thetransfer module, the first supercritical processing module includingfirst means for sealing the first supercritical processing module; d. asecond supercritical processing module coupled to the transfer module,the second supercritical processing module including second means forsealing the second supercritical processing module; and e. a transfermechanism coupled to the transfer module such that in operation thetransfer mechanism transfers first and second semiconductor substratesbetween the first and second supercritical processing modules,respectively, and the entrance of the transfer module.
 33. An apparatusfor supercritical processing of first and second workpieces comprising:a. a hand-off station; b. first and second supercritical processingmodules coupled to the hand-off station; and c. a transfer mechanismcoupled to the hand-off station, the transfer mechanism coupled to thefirst and second supercritical processing modules, the transfermechanism configured to move the first workpiece between the hand-offstation and the first supercritical processing module, the transfermechanism configured to move the second workpiece between the hand-offstation and the second supercritical processing module.